import sgmllib, string

class StrippingParser(sgmllib.SGMLParser):
	# These are the HTML tags that we will leave intact
	valid_tags = ()
	from htmlentitydefs import entitydefs # replace entitydefs from sgmllib
	def __init__(self):
		sgmllib.SGMLParser.__init__(self)
		self.result = ""
		self.endTagList = [] 
        
	def handle_data(self, data):
		if data:
			self.result = self.result + data

	def handle_charref(self, name):
		self.result = "%s&#%s;" % (self.result, name)
        
	def handle_entityref(self, name):
		if self.entitydefs.has_key(name): 
			x = ';'
		else:
			# this breaks unstandard entities that end with ';'
			x = ''
 		self.result = "%s&%s%s" % (self.result, name, x)
    
	def unknown_starttag(self, tag, attrs):
		""" Delete all tags except for legal ones """
 		if tag in self.valid_tags:       
 			self.result = self.result + '<' + tag
 			for k, v in attrs:
 				if string.lower(k[0:2]) != 'on' and string.lower(v[0:10]) != 'javascript':
					self.result = '%s %s="%s"' % (self.result, k, v)
			endTag = '</%s>' % tag
 			self.endTagList.insert(0,endTag)    
			self.result = self.result + '>'
                
	def unknown_endtag(self, tag):
		if tag in self.valid_tags:
 			self.result = "%s</%s>" % (self.result, tag)
 			remTag = '</%s>' % tag
			self.endTagList.remove(remTag)

	def cleanup(self):
		""" Append missing closing tags """
 		for j in range(len(self.endTagList)):
			 self.result = self.result + self.endTagList[j]    
        

def strip(s):
	""" Strip illegal HTML tags from string s """
    	parser = StrippingParser()
    	parser.feed(s)
    	parser.close()
    	parser.cleanup()
    	return parser.result
